Method for producing of ultra-clean and high-purity electronic grade acetic acid

ABSTRACT

A method for producing of ultra-clean and high-purity electronic acetic acid is disclosed. The method including following steps: Step 1, industrial acetic acid is fast distilled; Step 2, filtering the fraction by membrane of 0.05˜0.3 μm aperture; Step 3, rectification; Step 4, membrane filtration again. Due to the adoption of the technical scheme above, the ultra-clean and high-purity electronic grade acetic acid which purity is 99.8% is produced. The content of single metal ion is lower than 1 ppb and the content of particulates which is ≧0.5 μm is lower than 5 pcs/ml. The method of the invention will help to reduce energy consumption, to simplify the operation, and to achieve the high security.

FIELD OF THE INVENTION

The present invention relates to a method for producing of electronicchemical, and in particular to a method for producing of Ultra-clean andHigh-purity electronic grade acetic acid.

BACKGROUND OF THE INVENTION

Electronic grade acetic acid is one of important solvent andindispensable electronic chemical in the electronic industry. Someparticulates, metal ions, unreacted raw materials, and intermediateproducts or by-products will be in the acetic acid because of the rawmaterials and equipments used during production, transportation andstorage. The existence of these impurities, in particularly the metalions, can lead the OISF (Oxidation Induce Stacking Fault) so that the PNJunction Leakage Current increases, Breakdown occurs, and the life ofcurrent carrier shortens. Even a small quantity of metal ions orparticulates can destroy the whole circuit when the line width of theintegrated circuit is thin. Therefore the requirement for the purity ofthe electronic chemicals is more and more critical in order to keep thedevelopment of super large-scale integrated circuit, and the puritymeeting the demands of the nanometer-grade IC has become the trends forelectronic chemicals.

The key of production of liquid Ultra-clean and High-purity Reagents (orProcess Chemicals) such as acetic acid is keeping the content of theimpurities (such as metal ions etc.) and granularity and being inconformity with the standard of requirement. The main producing methodsinclude ionized sub-boiling distillation, azeotropic distillation,(multistage) rectification, and chemical treatment, etc. at the present.But there isn't a satisfactory method for producing of electronic gradeacetic acid.

Multistage rectification such as the two-stage rectification method andequipment disclosed in Chinese patent No. CN1285560C to produce theacetic acid to be in conformity with SEMI-C7 standard is the mostcommonly used method for producing of ultra-clean and high purity aceticacid. The long period and continuous production realizes with themultistage rectification, but there are still some defects such as heavyenergy consumption and high risk.

Chinese patent No. CN100372586C disclosed a method and equipment forproducing of ultra-clean and high-purity acid. The method and equipmentis composed by a barbed rectification tower and a filled tower in seriesto produce electronic acid such as hydrochloric acid, acetic acidimproves the conventional method and equipment. However, the internalstructure of this equipment is complicated.

SUMMARY OF THE INVENTION

The present invention provides a method for producing of ultra-clean andhigh-purity electronic grade acetic acid. The metal ions andparticulates can be removed effectively because of the combination ofthe distillation, membrane filtration, and rectification. And theultra-clean and high-purity electronic grade acetic acid is producedwith simple operation, low energy consumption and high safety.

The method of the invention for producing of ultra-clean and high-purityacetic acid includes following steps:

Step 1, fast distilling the industrial acetic acid and collect thefraction with the rate of ≧20 L/min to remove the unreacted rawmaterials, intermediate products or by-products; the optimized rate offraction collection is 20˜50 L/min.

Step 2, filtering the fraction collected in step 1 by membrane of0.05˜0.3 μm aperture;

Step 3, rectifying the colature and collect the fraction;

Step 4, filtering the fraction collected in step 3 by membrane of0.05˜0.3 μm aperture, and collect the colature to get the production.

In Step 1, the optimized distillation temperature is 130˜140° C.

In Step 2, the optimized membrane used is a β-cyclodextrin compositemembrane.

In Step 3, the optimized rectification is atmospheric rectificationunder 125˜135° C., and the fraction of 117.5˜118.5° C. is collected.

In Step 4, the optimized membrane used is an 18-crown-6 ether compositemembrane.

The optimized filter velocity of the filtration used the β-cyclodextrinor the 18-crown-6 composite membrane is 1˜5 L/h.

In the preferred embodiment, the rectification column in the presentinvention is a packed tower.

The optimized packing is the mixture of HDPE and PFA.

The optimized weight ratio between HDPE and PFA is 10˜15:1.

The method of the present invention removes most of organic impuritiessuch as formic acid and acetaldehyde through the fast distillationbefore rectification. And the cost of distillation is much lower thanrectification.

Because most of the impurities are removed, so the purity of the aceticacid when rectifying is increased. So the working difficulty of therectification is decreased by the greatest extent. And the energyconsumption and risk of the method are lower than conventional method.

The membrane filter used to remove metal ions is much simpler inoperation, lower cost and more environmentally friendly than therectification. And the filter does not remove the metal ions only, butalso remove the particulates.

The mixture of HDPE and PFA used as packing of the packed tower has theadvantage of good separating efficiency brought by PFA. Addition of HDPEdecreases the cost largely but doesn't decrease the separation result.

Overall, the method for producing of ultra-clean and high-purity aceticacid of the present invention has the advantage of simple operation, lowenergy consumption and low cost. The purity of the product is 99.8%, thecontent of single metal ion is lower than 1 ppb, and the content of theparticulates which is ≧0.5 μm is 2 pcs/ml.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the process of the method of the present invention,in which reference number 1 is the industrial acetic acid; referencenumber 2 is a distillation column; reference number 3 is a coolingcolumn; reference number 4 is a β-cyclodextrin composite membranefilter; reference number 5 is a rectifying column; reference number 6 isa cooling column; reference number 7 is an 18-crown-6 composite membranefilter; reference number 8 is a reservoir.

DETAILED DESCRIPTION OF THE INVENTION

A better understanding of the present invention is obtained when thefollowing non-limiting detailed description is considered in conjunctionwith FIG. 1.

Embodiment 1

Step 1, Industrial acetic acid is fast distilled to remove the unreactedraw materials and intermediate products or by-products generated duringsynthesis of acetic acid.

Most of the impurities can be removed through distillation, and the costis lower and the operation is simpler than rectification.

The temperature of distillation can be selected within the range of130˜140° C., and the rate of fraction collection in the range of 20˜50L/min to quicken the distillation, and to save the time and increaseproductivity.

Step 2, filtering the fraction collected in step 1 using membrane of0.05˜0.3 μm aperture. Keeping the filtration velocity in range of 1˜5L/h to avoid the breakage and the worse filtering result by the highpressure.

Step 3, rectifying the colature at 125˜135° C. and atmospheric pressure,and collecting fraction of 117.5˜118.5° C.

The packed tower with packing working as gas-liquid contactor can beused as the rectification column because of its advantage of high yieldand separation efficiency, low energy consumption, small pressure loss,etc.

The packing that supplies the gas-liquid contact surface to mass andheat transfer is the core of the packed tower. PFA (Polyfluoroalkoxy)which is the polymer of corrosion resistance and high temperatureresistance leads the good separating efficiency as packing.

The mixture of HDPE (High Density Polyethylene) and PFA can be used aspacking also. And the optimized weight ratio between HOPE and PFA is10˜15:1. The cost of the packing reduces to 1/50˜ 1/100 because of thelow-cost of the HDPE. And the addition of HDPE does not decrease theadvantage of good separating efficiency of PFA.

Step 4, filtering the fraction collected in Step 3 through the membraneof 0.05˜0.3 μm aperture and collecting the colature to get theultra-clean and high-purity electronic grade acetic acid.

And it is similar in Step 2, the filtration velocity is in range of 1˜5L/h.

The metal ions are removed by rectification and particulates by themembrane filter, and the ultra-clean and high-purity acetic acid isproduced.

Embodiment 2

Step 1, industrial acetic acid is fast distilled to remove the unreactedraw materials and intermediate products or by-products generated duringsynthesis of acetic acid. Collect fraction.

Step 2, filtering the fraction collected in Step 1 through using theβ-cyclodextrin composite membrane. The filtration velocity is kept inrange of 1˜5 L/h.

The molecule of a β-cyclodextrin that is a cyclic oligosaccharide, it istubbish or tubular. And the β-cyclodextrin composite membrane can removethe heavy metal ions because of the particularly molecule structure.

Hence, the particulates, and some metal ions simultaneity, are removedby the β-cyclodextrin composite membrane. And the difficulty of the nextrectification is reduced.

The production of the β-cyclodextrin composite membrane is: Solid Kaolinclay, main constituents of which are SiO₂, Al₂O₃ and H₂O, is grindedwith the β-cyclodextrin to 200˜300 mesh fines, and mixed homogeneouslywith binder (polyvinyl alcohol for example) to get base (semifinishedproduct). The base is dried at a low temperature and sintered at200˜250° C. to get 0.05˜0.3 μm aperture composite membrane of theβ-cyclodextrin and Kaolin clay carrier.

Step 3, rectifying the colature at 125˜135° C. and the atmosphericpressure, and collecting the fraction at 117.5˜118.5° C.

Step 4, filtering the fraction collected in step 3 using membrane of0.05˜0.3 μm aperture and keep the filtration velocity in range of 1˜5L/h.

Embodiment 3

Step 1, industrial acetic acid is fast distilled to remove the unreactedraw materials and intermediate products or by-products generated duringsynthesis of acetic acid; collecting the fraction.

Step 2, filtering the fraction collected in Step 2 through using themembrane of 0.05˜0.3 μm aperture and keeping the filtration velocity inrange of 1˜5 L/h.

Step 3, rectifying the colature at 125˜135° C. and atmospheric pressure,and collecting fraction at 117.5˜118.5° C.

Step 4, filtering the fraction collected in Step 3 through using an18-crown-6 ether composite membrane. Keeping the filtration velocity inrange of 1˜5 L/h.

The 18-crown-6 ether, which is also called1,4,7,10,13,16-hexaoxacyclooctadecane, is a crown ether. The diameter ofthe 18-crown-6 ether cyclic molecule is equivalent to the diameter ofpotassium ion. Therefore the 18-crown-6 ether can be complex with lightmetal ions such as potassium ion and sodium ion and remove these ions.Hence the particulates, and some residual metal ions after rectificationsimultaneity are removed.

The 18-crown-6 ether composite membrane can be produced by the methodfor the β-cyclodextrin composite membrane.

At last, the colature is collected to get the ultra-clean andhigh-purity acetic acid.

Embodiment 4

Step 1, industrial acetic acid is fast distilled to remove the unreactedraw materials and intermediate products or by-products generated duringsynthesis of acetic acid. And the fraction is collected with the rate of20˜50 L/min.

Step 2, filtering the fraction using β-cyclodextrin composite membrane.Keeping the filtration velocity in range of 1˜5 L/h.

Step 3, rectifying the colature at 125˜135° C. and atmospheric pressure,and collecting the fraction at 117.5˜118.5° C.

Step 4, filtering the fraction through using 18-crown-6 ether compositemembrane. Keeping the filtration velocity in range of 1˜5 L/h.

Collecting the colature to get the ultra-clean and high-purityelectronic grade acetic acid.

Detecting the purity of the acetic acid produced in Embodiment 4 withfollowing equipments: autotitrator for content of the acetic acid;ICP-MS for the content of the cations; turbidimeter and UltravioletSpectrophotometer for content of anions; and Laser Particle Counter forcontent of particulates. The testing result of the purity is listed intable 1.

TABLE 1 purity of the acetic acid produced in Embodiment 4 ParameterU.M. Result Assay(CH₃COOH) % 99.8 Color APHA 5 Chloride(Cl) ppb 121Sulfate(SO₄) ppb 234 Phosphate(PO₄) ppb 95 Residue After Evaporation ppb231 Acetic Anhydride % ≦0.1 Aluminum(Al) ppb 0.3 Arsenic(As) ppb 0.6Antimony(Sb) ppb 0.4 Barium(Ba) ppb 0.3 Beryllium(Be) ppb 0.7Bismuth(Bi) ppb 0.2 Boron(B) ppb 0.1 Cadmium(Cd) ppb 0.3 Calcium(Ca) ppb0.6 Chromium(Cr) ppb 0.3 Cobalt(Co) ppb 0.2 Copper(Cu) ppb 0.2Gallium(Ga) ppb 0.4 Germanium(Ge) ppb 0.5 Gold(Au) ppb 0.1 Indium(In)ppb 0.2 Ion(Fe) ppb 0.4 Lead(Pb) ppb 0.6 Lithium(Li) ppb 0.1Magnesium(Mg) ppb 0.3 Manganese(Mn) ppb 0.5 Molybdenum(Mo) ppb 0.4Nickel(Ni) ppb 0.3 Niobium(Nb) ppb 0.6 Potassium(K) ppb 0.3 Platinum(Pt)ppb 0.2 Silicon(Si) ppb 0.3 Silver(Ag) ppb 0.4 Sodium(Na) ppb 0.7Strontium(Sr) ppb 0.4 Tin(Sn) ppb 0.4 Tantalum(Ta) ppb 0.4 Titanium(Ti)ppb 0.4 Thallium(Tl) ppb 0.4 Zinc(Zn) ppb 0.5 Zirconium(Zr) ppb 0.3 ≧0.3μm particulates pcs/ml 123 ≧0.5 μm particulates pcs/ml 2 ≧1.0 μmparticulates pcs/ml none

According to the result in table 1, it can be seen that the purity ofacetic acid produced is 99.8%, the content of single metal ions is lowerthan 1 ppb, and the content of particulates which is ≧0.5 μm is 2pcs/ml. Therefore the product is in conformity with the standard of theultra-clean and high-purity electronic grade acetic acid.

The above description is the illustrations of application and thereagents, equipments, or operation and detection not mentioned shall bedeemed as the normal and routine ones in this field of technology.

It will be understood that the description of the embodiments above isonly the illustrations of application, and it does not limit theinvention to the specific embodiments illustrated. Numerous other waysof carrying out the method provided by the present invention may bedevised by the skilled in the art without departing from the scope ofthe invention, and they are thus encompassed by the present invention.Thus it should be understood that any identical shifting can be donewithout departing from the scope of the present invention.

1. A method for producing of ultra-clean and high-purity electronicgrade acetic acid characterizes that the method includes followingsteps: Step 1, distilling the industrial acetic acid fast, and collectthe fraction with the rate of ≧20 L/min; Step 2, filtering the fractioncollected in step 1 through a membrane of 0.05˜0.3 μm aperture; Step 3,rectifying the colature and collecting the fraction; Step 4, filteringthe fraction collected in step 3 through a membrane of 0.05˜0.3 μmaperture, and collecting the colature to get the production.
 2. A methodaccording to claim 1, characterized in that the fraction is colletedwith the rate of 20˜50 L/min in step
 1. 3. A method according to claim2, characterized in that the temperature of distillation is 130˜140° C.4. A method according to claim 1, characterized in that the membraneused in step 2 is a β-cyclodextrin composite membrane.
 5. A methodaccording to claim 1, characterized in that the membrane used in step 4is an 18-crown-6 ether composite membrane.
 6. A method according toclaim 4 or 5, characterized in that the filter velocity of thefiltration used the membrane is 1˜5 L/h.
 7. A method according to claim1, characterized in that the colature is rectified under 125˜135° C. andnormal atmosphere, and the fraction of 117.5˜118.5° C. is collected. 8.A method according to claim 7, characterized in that the rectifyingcolumn used in step 3 is a packed tower.
 9. A method according to claim8, characterized in that the packing in the packed tower is the mixtureof HDPE and PFA.
 10. A method according to claim 9, characterized inthat the weight ratio between HDPE and PFA is 10˜15:1.